In recent years, the Quetta Valley and surrounding areas have experienced unprecedented levels of subsidence, which has been attributed mainly to groundwater withdrawal. However, this region is also tectonically active and is home to several regional strike-slip faults, including the north–south striking left-lateral Chaman Fault System. Several large earthquakes have occurred recently in this area, including one deadly Mw 6.4 earthquake that struck on 28 October 2008. This study integrated Interferometric Synthetic Aperture Radar (InSAR) results with GPS, gravity, seismic reflection profiles, and earthquake centroid-moment-tensor (CMT) data to identify the impact of tectonic and anthropogenic processes on subsidence and earthquake patterns in this region. To detect and map the spatial-temporal features of the processes that led to the surface deformation, this study used two Synthetic Aperture Radar (SAR) time series, i.e., 15 Phased Array L-band Synthetic Aperture Radar (PALSAR) images acquired by an Advanced Land Observing Satellite (ALOS) from 2006–2011 and 40 Environmental Satellite (ENVISAT) Advanced Synthetic Aperture Radar (ASAR) images spanning 2003–2010. A Small Baseline Subset (SBAS) technique was used to investigate surface deformation. Five seismic lines totaling ~60 km, acquired in 2003, were used to map the blind thrust faults beneath a Quaternary alluvium layer. The median filtered SBAS-InSAR average velocity profile supports groundwater withdrawal as the dominant source of subsidence, with some contribution from tectonic subsidence in the Quetta Valley. Results of SBAS-InSAR multi-temporal analysis provide a better explanation for the pre-, co-, and post-seismic displacement pattern caused by the 2008 earthquake swarms across two strike-slip faults.

No abstract

No abstract

No abstract

We report on a suite of geophysical surveys conducted on glacial sediments near Red Lodge, Montana. The University of Houston (with assistance from University of Calgary, GEDCO, and UT-Austin personnel) conducted VSP and well log surveys in the 115m-deep, PVC-cased water well, GB-1, located on the glacial benches. The multi-offset VSP was undertaken using surface sources (an accelerated weight drop and sledge hammer) with a hydrophone string and downhole, wall-clamping, 3component geophone. The well logs included measurements of conductivity, radioactivity (gamma ray), temperature, and sonic velocity. Sonic and VSP velocities ranged from 1500m/s in the very near surface to 3000m/s at 85m depth. A distinct black clay layer (with high conductivity, high gamma ray, and low velocity) was penetrated at 85m. High-resolution 2D and 3D seismic surveys, using a sledge hammer source, showed a number of reflectors to about 150ms two-way traveltime. On the Lplot composite displaying well log data, synthetic seismograms, and the VSP corridor stack, a reflection at 80ms correlated with the 85m interface Various other reflections in the VSP and surface seismic data were interpreted to represent glacial deposit layers and water zones (from the perforation logs).